In fabricating optical and optoelectronic devices, optical components need to be firmly attached to a substrate within the path of light. Such devices include lasers, p-i-n diodes, and assemblies of such devices with passive elements such as planar waveguides. Presently, methods for attaching the optical components to a substrate include aluminum oxide ("ALO") bonding, solder bonding, and solder-glass bonding. ALO bonding methods present many technical difficulties, including the need for high temperatures and high stress which have a tendency to produce defects such as cracks that can remain hidden for a long time and cause reliability problems. Another method of attachment includes epoxy bonding, but this has the disadvantage of relying upon use of organic materials which, when applied to optical components, can promote facet failure or moisture which likewise creates reliability problems.
Bonding of optical components is further complicated because the components often include objects such as spherical ball and cylindrical lenses which, due to their smooth outer surfaces, are difficult to handle. Soldering of the components requires depositing a metallization layer on their surfaces, which destroys the symmetry of the components and increases handling problems. Optical components used in laser communications systems or other systems involving gain media may be required to have specialized asymmetrical coatings on their surfaces for specific purposes, such as the avoidance of circulating rainbow or "whispering gallery" modes of spherical lenses, which can cause excess feedback and self-modulation. These asymmetrical components are particularly difficult to handle, as they often must be carefully attached during assembly on a substrate with the asymmetrical feature oriented in a precise alignment relative to the path of light. Challenges have been encountered in developing apparatus capable of placing the components with the required precision and also applying the pressure to them needed for bonding, as described, for example, in U.S. Pat. No. 5,194,105 issued Mar. 16, 1993, to Nguyen entitled "Placement and Bonding Technique for Optical Elements," assigned to AT&T Co., the predecessor of the assignee herein, which is hereby incorporated by reference. Pick-and-place tools for manual orientation and placement of optical components can be slow and expensive.
Given these challenges encountered with present methods of attachment, it is desirable to provide an optical component and method for attaching the optical component that minimizes difficulties associated with manually, precisely orienting the component. Advantageously, this method should exhibit high reliability and be compatible with existing technologies, such as solder bonding or thermocompression, already in use in packaging. The instant invention addresses these needs by providing a substantially self-orienting optical component which aids in assembly and methods for assembling a sub-optical assembly comprising passively orienting the component. Further advantages may appear more fully upon consideration of the description given below.